Triaryl borane catalysts and method for selective hydrosilylation of esters and lactones using catalysts

Abstract

To provide a use for novel triaryl borane type catalyst compounds which can be applied for the partial reduction of an ester or lactone to a silyl acetal.SOLUTION: The present invention relates to a use of compounds of general formula (Ia) as catalysts for partial reduction of a carbonyl group in an ester substrate or lactone substrate, wherein the substrate contains one or more functional group(s) independently selected from the group consisting of non-carbonyl-conjugated olefinic bonds, non-carbonyl-conjugated acetylenic bonds, ether, amide, and halogen groups.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalytic process for the partial reduction of esters or lactones to silyl acetals, which upon hydrolysis give aldehydes or lactols, using a silane, such as triethylsilane (TESH), as a reducing agent in the presence of a novel triarylborane-type catalyst.

[0002] More specifically, the present invention relates to novel triarylborane-type catalyst compounds of formula (I) (see below) that can be applied to the partial reduction of esters or lactones to silyl acetals. The present invention also relates to a process for preparing aldehydes or lactols, said process comprising the steps of: i) reacting an ester or lactone with a silane in the presence of a compound of formula (I) to give a silyl acetal, ii) hydrolyzing the obtained silyl acetal with an acidic or fluoride-containing reagent to form an aldehyde or lactol, and iii) optionally isolating and purifying the obtained aldehyde or lactol. [Background technology]

[0003] Aldehydes and lactols are useful products in the cosmetic and agrochemical industries, but they are also important intermediates for the preparation of fine chemicals, especially in the pharmaceutical industry. Because esters and lactones are readily available and relatively inexpensive starting materials, the selective reduction of ester functional groups to the corresponding aldehydes is one of the fundamental reactions in organic chemistry and is used in many chemical processes. To avoid overreduction to alcohols, the reaction should terminate at the acetal intermediate; i.e., the reaction of silanes should occur only at the C=O functional group. To date, hydride reducing agents, such as diisobutylaluminum hydride (DIBAL-H) ​​or lithium tri-tert-butoxyaluminum hydride, have been used exclusively. The use of these reagents is expensive because the reaction must be carried out at low temperatures to minimize overreduction to alcohols. Furthermore, they exhibit drawbacks such as high flammability, violent reactions with water releasing highly flammable gases, spontaneous flammability in air, and difficult workup procedures.Nevertheless, when overreduction to the alcohol cannot be avoided with these two reagents, an indirect two-step protocol is used to obtain the required aldehyde: overreduction of the ester to the alcohol, followed by selective oxidation of the alcohol to the aldehyde [Dess, D.B.; Martin, J.C. (1983), “Readily accessible 12-I-5 oxidant for the conversion of primary and secondary alcohols to aldehydes and ketones” J. Org. Chem. 48, 4155; Omura, K.; Swern, D. (1978), “Oxidation of alcohols by 'activated' dimethyl sulfoxide. A preparative, steric, and mechanistic study” Tetrahedron. 34, 1651; Barriga, S. (2001), “2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO)” Synlett 563; Montanari, F.; Quici, S.; Henry-Riyad, H.; Tidwell, TT (2005), “2,2,6,6-Tetramethylpiperidin-1-oxyl” Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. This indirect approach is often the only option, but is far from economical as a result of poor redox economics.

[0004] In addition to non-catalytic processes, catalytic reduction of esters to aldehydes is also known. Thus, several publications describe the use of silanes as alternative reducing agents for ester substrates, together with metal and even some non-metallic catalysts. Preferred silanes for these types of reductions are triphenylsilane (PhSiH), diethylsilane (EtSiH), or triethylsilane (EtSiH).

[0005] Piers et al. [Parks, DJ; Blackwell, JM; Piers, WE (2000), "Studies on the Mechanism of B(CF)-Catalyzed Hydrosilation of Carbonyl Functions," J. Org. Chem. 65, 3090] reported the reduction of esters to silyl acetals using PhSiH and the nonmetallic catalyst tris(pentafluorophenyl)borane B(CF). This process can be used for a variety of substrates, but these reactions were accompanied by substantial overreduction (5–30%) to silyl ethers and alkanes. Japanese Patent Application No. 2016084310 (Kazumasa) describes a similar method for reducing α-fluorinated esters to fluorinated silyl acetals using a system consisting of a silane reducing agent and a B, Al, or Ti Lewis acid. Among the preferred catalysts, tris(pentafluorophenyl)borane B(CF) is used in the patented method. Such catalysts are said to be suitable for the selective partial reduction of α-fluorinated esters to silyl acetals at least 1 mol % relative to the substrate. Importantly, this process is limited to esters bearing electron-withdrawing substituents at the α-position.

[0006] The use of a BAC'-type (i.e., as shown below) triarylborane, namely mesitylbis(perfluorophenyl)borane (Mes(F5)2 borane), as a catalyst for the partial reduction of ester functionality has been reported in Fegyverneki's doctoral dissertation [D. Fegyverneki (2018), "Szililvegyuletek atalakitasa triaril-boran Lewis-savakkal" doctoral dissertation, Eotvos Lorand University]. Each method demonstrated the capability of borane-mediated hydrosilylation of multiple ester substrates, achieving yields of 31–99% using 5 mol% of the catalyst and 1 equivalent of triethylsilane (Et3SiH) as the reducing agent. The resulting silyl acetals were further converted to aldehydes, yielding 50–81%. Despite promising results, the reported Mes(F5)2 borane catalyst lacks the advantageous structural, electronic, and steric properties of the novel catalysts presented in this invention. As a result, higher catalyst loadings and longer reaction times were required, leading to lower yields compared to processes applying the catalyst according to the invention. This is also supported by comparative studies seen in Table 1: when Mes(F5)2 borane was used under the same reaction conditions, a significantly lower yield (3.4%) was detected (see, for example, item 6) compared to the results obtained with the catalyst presented in this invention (over 85%).

[0007] Silyl acetal [Motoyama Y et al. (2018), “Catalytic Silane-Reduction of Carboxylic Esters and Lactones: Selective Synthetic Methods to Aldehydes, Lactols, and ethers via Silyl Acetyl Intermediates” Chemistry Select, 3, 2958; Sortais B. and Darcel C. et al (2013), “Selective Reduction of Esters to Aldehydes under the Catalysis of Well-Defined NHC-Iron Complexes” Angew. Chem. Int. Ed. 52, 8045; Wei. D and Sortais JB (2020), “Manganese and Rhenium-catalyzed Selective Reduction of Esters to Aldehydes with Hydrosilanes” Chem. Commun, Among the few metal-based catalysts or catalytic systems known to selectively reduce esters to aldehydes, the Ir-catalyzed procedure developed by Cheng and Brookhart [Cheng, C. and Brookhart, M. (2012), “Efficient Reduction of Esters to Aldehydes through Iridium-Catalyzed Hydrosilylation,” Angew. Chem. Int. Ed. 51, 9422.] deserves special mention. Compared to other metal-based catalytic systems, this system requires a small amount of catalyst (approximately 0.1–0.5 mol%) and reducing agent, Et2SiH2. However, this method uses a toxic and expensive catalyst. Furthermore, no ester substrates bearing olefinic functional groups have been reported.

[0008] Although reagents and processes for the partial reduction of substrates bearing an ester or lactone functionality are known in the art, there remains a need for alternative, industrially acceptable reagents and processes for producing aldehydes or lactols from substrates containing ester groups. Particularly suitable for this purpose are alternative catalysts that allow the process to proceed with low catalyst loading, high conversion, and high chemoselectivity for molecules containing ester functionality and that allow the use of mild experimental conditions (temperatures of about 25-50°C, ambient atmosphere, i.e., without the exclusion of oxygen and humidity).

[0009] Few compounds are known that fall within the scope of general formula (I) but have different utility. These compounds are excluded by the so-called "disclaimer / disclaimer" section at the end of claim 1. The excluded compounds are described in the following prior art documents:

[0010] Koster et al. (1963), "Umwandlungen bororganischer Verbindungen in der Hitze" Angew. Chem., 75, 1079-1090, discloses the synthesis of triarylboranes bearing o-biphenylylaryl groups. However, this compound is used only as an intermediate for the synthesis of 9-borafluorene, without considering its use as a catalyst in organic reactions.

[0011] WO 2019 / 004172 proposes a BA2C-type borane having an o-tolylaryl group as a substituent. This compound is then used as a catalyst in the production of organoxysiloxanes by reacting siloxanes with alcohols. However, this reactivity does not provide any clues as to the potential use of the borane compound as a catalyst for the partial reduction of ester and lactone moieties.

[0012] Furthermore, a compound with a similar structure has been disclosed in the following paper: Liting Li et al. (2000), "Bis(Pentafluorophenyl)(2-perfluorobiphenylyl)borane. A New Perfluoroarylborane Cocatalyst for Single-Site Olefin Polymerization," Organometallics, 19, 3332-3337, see 2-perfluorobiphenylyl group (one of the groups ortho to the boron atom is a small group (F), and the other ortho group is a large group (pentafluorophenyl)). However, this compound is only applicable as a catalyst in olefin polymerization, and there is no suggestion in this paper that it can be specifically applied as a catalyst in the reduction of esters and lactones to aldehydes and lactols. Also, a similar borane with a methyl group as the large ortho substituent has been described by Ziegler et al. (2005), "Possible Thermal Decomposition Routes in [MeB(CF)] - [L2TiMe + ] as Deactivation Pathways in Olefin Polymerization Catalysis: A Combined Density Functional Theory and Molecular Mechanics Investigation” Organometallics, 24, 2076-2085, but only as a pyrolysis by-product of B(C6F5)3-catalyzed olefin polymerization. Both of these referenced studies and the respective boranes can be found in the review article Melen et al. (2020) “Halogenated triarylboranes: synthesis, properties, and applications in catalysis” Chem. Soc. Rev., 49, 1706-1725. The possibility of using these boranes as catalysts for the hydrosilylation of esters and lactones is also not given here.

[0013] Chinese Patent No. 111574543 presents BAA'C-type (see below) boranes with chlorine as the bulky ortho-substituent. However, each borane is used only as a starting material for the construction of larger polycyclic compounds that can be used in organic electroluminescent devices. The scope of the patent does not concern the use of triarylboranes as catalysts.

[0014] WO 2019 / 055727 presents two BA2C-type boranes, the bulky ortho-substituents of which are Cl and CF3 groups, respectively. These compounds were used as Lewis acidic polymerization catalysts for the production of polyether polyols. This document does not provide any hints about their possible use for the partial reduction of esters and lactones.

[0015] In his doctoral dissertation, J. Bortoluzzi [J. Bortoluzzi (2018), “Biphenyles a chiralite axiale: vers la synthèse de paires de Lewis frustrees pour la catalyse enantioselective” doctoral dissertation, Universite de Strasbourg] presented the synthesis of racemic biphenylboranes of the BAC type. However, the potential application of this compound in catalytic hydrosilylation reactions was not investigated.

[0016] Finally, Hoshimoto et al. (2018) "Main-Group-Catalyzed Reductive Alkylation of Multiply Substituted Amines with Aldehydes Using H2," J. Am. Chem. Soc., 140, 7292-7300, presents a triarylborane bearing a CF3 group as a bulky ortho-substituent. This compound was then used as a catalyst for the reductive alkylation of amines using hydrogen gas as the reducing agent. Importantly, this application does not provide any insight into the potential use of boranes as catalysts for the partial reduction of esters and lactones.

[0017] As mentioned above, the inventors emphasize that none of these documents contain any hints regarding the surprising effects and properties of the catalysts of the present invention. It is important to emphasize that the use of these compounds in a particular type of catalytic reaction makes it unlikely that the catalyst can also be applied to a different type of catalytic reaction. Summary of the Invention [Problem to be solved by the invention]

[0018] The technical problem solved by the present invention is to provide a triarylborane-type catalyst for the selective hydrosilylation of esters or lactones, the use of which in the hydrosilylation of esters or lactones has the following characteristics: a) low catalyst loading, b) high conversion rate; c) high chemoselectivity for molecules containing ester functional groups, in particular reducing esters of unsaturated fatty acids from natural sources without any modification of the position or stereochemistry of the olefinic double bond; d) low overreduction of esters and lactones to silyl ethers; so low that purification of the crude product is often not necessary; e) Mild operating conditions.

[0019] Inventive discovery During our experiments, we surprisingly found that the above requirements can be achieved by using such triarylborane-type catalysts in which the aryl groups have a special substituent pattern. That is, in two aryl groups, only small groups (e.g., H, D, and F atoms) should be in the ortho positions (the ortho positions are related to the bond connecting to the boron atom), and in the third aryl group, similar small groups should be present in one of the ortho positions (e.g., H, D, and F atoms), while a larger group (with greater steric demands) should be present in the other (e.g., Cl, Br, I, SF5, alkyl, alkenyl, cyclic alkyl, cyclic alkenyl, aryl, or heteroaryl) (ortho position as defined above). The other substituents are of secondary importance, but ensure the optimal Lewis acidity properties of the catalyst molecule. In particular, the optimal Lewis acidity is in a range dictated by the substrate. When more basic (oxygen Lewis basic) esters or lactones are reduced, lower Lewis acidity is required to reach high selectivity (to suppress over-reduction), and when less Lewis basic esters (e.g., α-fluorinated, chlorinated) are reduced, higher Lewis acidity is required (to promote Si-H bond activation). [Means for solving the problem]

[0020] 1. Thus, in a first aspect, the present invention provides compounds of general formula (I): [ka] (In the formula, B is boron; ring A and ring A' are each independently an aryl or heteroaryl group; R1 and R'1 are independently selected from groups with small steric demands, preferably H, D and F; R5 and R'5 are independently selected from groups with small steric demands, preferably H, D and F; each R2, R3, R4, R'2, R'3 and R'4 is independently selected from the group consisting of H, D, F, Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; Ring C is an aryl group, R6 is selected from groups with small steric demands, preferably H, D and F; R 10 is a group with high steric demand, preferably Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl and Si(R 15 ) groups, wherein alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; R 15 The groups are, independently of one another, selected from the following range: alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; R7, R8, and R9 are independently selected from the group consisting of H, D, F, Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; however, When R1 to R5, R'1 to R'5 and R6 to R9 are F, R 10 is not a pentafluorophenyl group or a methyl group; When R1 to R5, R'1 to R'5 and R6 to R9 are H, R 10 is not phenyl; When R1 to R5 and R'1 to R'5 are F and R6 to R9 are H, R 10 is not methyl; When R1 to R5, R'1, R'3, R'4, R'5, R6, R7, and R8 are H, and R'2 and R9 are Br, R 10 is not Cl; When R1, R5, R1′ and R5′ are H, R2, R4, R2′ and R4′ are CF3, R6 and R8 are F, and R7 and R9 are H, then R 10 is not Cl; R1, R5, R1' and R5' are H, R2, R4, R 2’ , R 4’ , when R6 and R9 are CF3, R 10 is not H; R1, R2, R4, R5, R 1’ R 2’ , R 4’ and R 5’ F, R 3’ , when R3, R6, R7 and R8 are H and R9 is Cl, R 10 is not 2-Br-phenyl; R1, R2, R4, R5, R 1’ R 2’ , R 4’ and R 5’ F, R 3’ , when R3, R6, R7, R8 and R9 are H, R 10 is not CF3)

[0021] 2. Another object of the present invention is the use of compounds of general formula (I): [ka] (In the formula, B is boron; ring A and ring A' are each independently an aryl group; R1 and R'1 are independently selected from groups with small steric demands, preferably H, D and F; R5 and R'5 are independently selected from groups with small steric demands, preferably H, D and F; each R2, R3, R4, R'2, R'3 and R'4 is independently selected from the group consisting of H, D, F, Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; Ring C is an aryl group, R6 is selected from groups with small steric demands, preferably H, D and F; R 10 is a group with large steric demand, preferably Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl and Si(R 15 ) groups, wherein alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; R 15 The groups are, independently of one another, selected from the following range: alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; R7, R8 and R9 are independently selected from the group consisting of H, D, F, Cl, Br, I, SF5, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; The substrate optionally contains one or more functional groups independently selected from the group consisting of a non-carbonyl conjugated olefinic bond, a non-carbonyl conjugated acetylenic bond, an ether, an amide, and a halogen group as a catalyst for the partial reduction of a carbonyl group in an ester substrate or a lactone substrate.

[0022] 3. In a preferred embodiment of the present invention, the compound of point 1 or 2 above may be characterized by the general formula (Ia): [ka] (In the ceremony Rings X and X′ are phenyl groups; R1 and R'1 are independently selected from the group consisting of H, D and F; R5 and R'5 are independently selected from the group consisting of H, D and F; each R2, R3, R4, R'2, R'3 and R'4 is independently selected from the group consisting of H, D, F, Cl, Br, alkyl, cycloalkyl and aryl groups, wherein the alkyl, cycloalkyl and aryl groups are optionally substituted; The Y ring is a phenyl group; R6 is selected from the group consisting of H, D and F; R 10 is selected from the group consisting of Cl, Br, I, SF5, alkyl, cycloalkyl, and aryl groups, wherein the alkyl, cycloalkyl, and aryl groups are optionally substituted; R7, R8, and R9 are independently selected from the group consisting of H, D, F, Cl, Br, alkyl, and cycloalkyl groups, wherein the alkyl and cycloalkyl groups are optionally substituted.

[0023] 4. In a further preferred embodiment of the present invention, the compounds of points 2 and 3 above have the following substituent meanings: The X and X' rings are phenyl groups, and each of R, R', R, and R' is F; and each of R, R, R, R, R, and R is independently selected from H and F; The Y ring is a phenyl group and R6 is selected from H and F; R 10 is selected from Cl, Br, methyl, and pentafluorophenyl groups; R7, R8, and R9 are independently selected from H and F.

[0024] 5. In a further preferred embodiment of the present invention, the compounds of point 3 or 4 above have the following substituent meanings: X and X' are independently selected from the group consisting of pentafluorophenyl, 2,3,4,6-tetrafluorophenyl, 2,3,5,6-tetrafluorophenyl, 2,4,6-trifluorophenyl, 2,3,6-trifluorophenyl, and 2,6-difluorophenyl groups.

[0025] 6. In a further preferred embodiment of the present invention, the compounds of any one of points 3 to 5 above have the following substituent meanings: Y is selected from the group consisting of 2-chloro-6-fluorophenyl, 2-bromo-6-fluorophenyl and perfluoro-1,1'-biphenyl-2-yl groups.

[0026] 7. In a further preferred embodiment of the present invention, the compound of any one of points 3 to 6 above is selected from the following group: (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 1); (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2); (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (compound 3); (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,4,6-trifluorophenyl)borane (compound 4); (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (compound 5); (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 6); and (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 7); Perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,6-trifluorophenyl)borane (compound 8).

[0027] 8. In a more preferred embodiment of the present invention, the compound of point 7 above is selected from the following group: (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 1); (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2); (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (compound 3); (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,4,6-trifluorophenyl)borane (compound 4); (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 6).

[0028] 9. A further object of the present invention is a catalytic process for the preparation of aldehydes or lactols by partial reduction of a carbonyl group in an ester or lactone substrate, wherein the substrate optionally contains one or more functional groups independently selected from the group consisting of a non-carbonyl conjugated olefinic bond, a non-carbonyl conjugated acetylenic bond, an ether, an amide, and a halogen group, the process comprising the steps of: a) reacting the ester or lactone substrate with a silane in the presence of a catalytic amount of a compound of formula (I) as defined in any one of the preceding claims to form a silyl acetal; b) hydrolyzing the resulting silyl acetal with one or more acidic or fluoride-containing reagents to form an aldehyde or lactol; c) optionally isolating and purifying the resulting aldehyde or lactol; The method includes:

[0029] In a preferred embodiment, the functional group of the substrate is selected from the group of non-carbonyl conjugated olefinic bonds, halogens and ether functional groups.

[0030] The preferred embodiments mentioned in points 2-7 are preferred embodiments of the subject matter discussed in points 8 and 9.

[0031] 10. As a further object, the present invention provides a compound of general formula (II): [ka] (In the formula, X is a halogen selected from the group consisting of Cl and Br; E is (CH2) m or (CH2) n -O-(CH2) p wherein m is an integer of 2 to 12, n and p are each independently an integer of 1 to 5, (CH2) m or (CH2) n -O-(CH2) p any one of the methylene groups may be optionally substituted with one or more substituents [e.g., 1 to 5, or 1 to 4, or 1 to 3, or 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl or trifluoromethyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R 11 is a trialkylsilyl or dialkylsiloxysilyl group, the alkyl portion of which is optionally substituted C 1-6 Alkyl groups, preferably C 1-4 is an alkyl group; R 12 is an optionally substituted alkyl group, preferably C 1-6 Alkyl groups, preferably C 1-3 alkyl group)

[0032] 11. In a preferred embodiment of the present invention, the compounds of point 10 above have the following substituent meanings: X is a halogen selected from the group consisting of Cl and Br; E is (CH2) m or (CH2) n -O-(CH2) p wherein m is an integer of 2 to 10, n and p are each independently an integer of 1 to 3, and ((CH2) mor (CH2) n -O-(CH2) p any one of the methylene groups may be optionally substituted with 1 to 3 substituents [e.g., 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R 11 is a trialkylsilyl or dialkylsiloxysilyl group, the alkyl portion of which is C 1-2 an alkyl group, preferably triethylsilyl; R 12 is C 1-3 It is an alkyl group, preferably a methyl, ethyl, propyl or isopropyl group.

[0033] 12. In a further preferred embodiment of the present invention, the compound of point 10 or point 11 above is selected from the following group: (4-Bromo-1-ethoxybutoxy)triethylsilane (Example 14) (3-Bromo-1-ethoxypropoxy)triethylsilane (Example 15) ((5-Bromo-1-ethoxypentyl)oxy)triethylsilane (Example 16) ((6-Bromo-1-ethoxyhexyl)oxy)triethylsilane (Example 17) (4-Bromo-1-isopropoxybutoxy)triethylsilane (Example 18) (2-(2-chloroethoxy)-1-ethoxyethoxy)triethylsilane (Example 19) (2-(2-bromoethoxy)-1-ethoxyethoxy)triethylsilane (Example 21) (4-Bromo-1-ethoxy-2-fluorobutoxy)triethylsilane (Example 22) ((4-Bromo-1-ethoxypentyl)oxy)triethylsilane (Example 24) (4-Bromo-1-ethoxy-2,2-difluorobutoxy)triethylsilane (Example 25) (4-Bromo-1-ethoxy-2-methylbutoxy)triethylsilane (Example 26).

[0034] 13. As a further object, the present invention provides a compound of general formula (III): [ka] (In the formula, X is a halogen selected from the group consisting of Cl and Br; G is (CH2) m or (CH2) n -O-(CH2) p wherein m is an integer of 2 to 12, n and p are each independently an integer of 1 to 5, (CH2) m or (CH2) n -O-(CH2) p any one of the methylene groups may be optionally substituted with one or more substituents [e.g., 1 to 5, or 1 to 4, or 1 to 3, or 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl or trifluoromethyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R 13 is an optionally substituted alkyl group, preferably C 1-6 an alkyl group, more preferably a methyl group; R 14 is an optionally substituted alkyl group, preferably C 1-6 Alkyl groups, more preferably C 1-3 alkyl group)

[0035] 14. In a preferred embodiment of the present invention, the compounds of point 13 above have the following substituent meanings: X is a halogen selected from the group consisting of Cl and Br; G is (CH2) m or (CH2) n -O-(CH2) p wherein m is an integer of 2 to 10, n and p are each independently an integer of 1 to 3, and ((CH2) mor (CH2) n -O-(CH2) p any one of the methylene groups may be optionally substituted with 1 to 3 substituents [e.g., 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R 13 is an optionally substituted alkyl group, preferably C 1-3 an alkyl group, more preferably a methyl group; R 14 is an optionally substituted alkyl group, preferably C 1-3 It is an alkyl group, more preferably a methyl, ethyl, propyl or isopropyl group.

[0036] 15. In a further preferred embodiment of the present invention, the compound of point 13 or point 14 above is 4,10-bis(3-bromopropyl)-6,6,8,8-tetramethyl-3,5,7,9,11-pentaoxa-6,8-disilatridecane (Example 27).

[0037] Detailed Description of the Invention During our research, we investigated the hydrosilylation reaction of esters using different frustrated Lewis pair (FLP)-based borane catalysts (Stephan, DW; Erker, G. (2015) “Frustrated Lewis Pair Chemistry: Development and Perspectives” Angew. Chem. Int. Ed., 54, 6400). Methyl 3-phenylpropionate was selected as a model compound, and its reduction was carried out with triethylsilane (TESH, the preferred silane compound) according to the following reaction scheme: [ka]

[0038] From the viewpoint of the applicability of the present method, it is important to point out the most important side reaction, namely the over-reduction of the formed silyl acetal to a silyl ether (the associated alcohol being formed by hydrolysis), according to the following reaction scheme: [ka]

[0039] Suppressing this side reaction is almost as important as achieving high conversion and yield. This can be particularly important in certain pheromone syntheses, where purification of the alcohol by-product is challenging for long-chain unsaturated fatty acid-derived sex pheromone aldehydes. Alcohol impurities are relevant because most of them act as behavioral antagonists. See, for example, Xu et al. (2016): "Olfactory perception and behavioral effects of sex pheromone gland components in Helicoverpa armigera and Helicoverpa assulta," Sci. Rep. 6, 22998. Therefore, the alcohol content in the reaction product cannot exceed a certain level in the final product for pheromone applications. Therefore, suppressing overreduction (preferably with nearly exclusive selectivity for silyl acetal formation) is a key technical feature in economically important application areas.

[0040] The present invention is based on the surprising finding that the use of electronically enabled, specially functionalized borane catalysts with specific electronic and steric properties significantly enhances reactivity and selectivity in the hydrosilylation of esters and lactones. The advantageous electronic and steric properties are the result of a special substituent pattern: in BAA'C-type boranes, the A and A' aryl (preferably phenyl) groups have only small groups (e.g., H, D, and F atoms) in the ortho positions, while the third aryl group (C, preferably phenyl) must have a similar small group (e.g., H, D, and F atoms) in one of the ortho positions and a larger group (with greater steric demands) in the other ortho position (e.g., Cl, Br, I, SF5, alkyl, alkenyl, cyclic alkyl, cyclic alkenyl group, aryl, aryl halide (preferably trifluoro-, tetrafluoro-, or pentafluoro(i.e., perfluoro-)phenyl, more preferably perfluorophenyl) or heteroaryl group, preferably Cl, Br, I, trifluoro-, tetrafluorophenyl, or perfluorophenyl or methyl group, more preferably Br) (ortho position as defined above). The larger group can be Si(R 15 ) groups, and R 15 The groups are selected independently from one another from the following ranges: alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, alkyl groups and in particular methyl groups are preferred.

[0041] It is noted here that, theoretically, the -OCF3 group could also behave as a small size group without weakening the acidic properties of the borane due to the electron-withdrawing effect of the fluorine atom.

[0042] As mentioned above, the other substituents are of secondary importance, but they should ensure the necessary Lewis acidic properties for the boron atom. For this reason, most of them must be electron-withdrawing groups, such as F and / or Cl atoms. If not all groups are electron-withdrawing groups (which is also possible, see perfluorinated rings), the remaining substituents can be selected, for example, from the group consisting of H, D, alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, where the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted, preferably H, D, alkyl, and aryl, more preferably H and alkyl, such as H.

[0043] In advantageous embodiments, the A and A' aryl groups are equivalent groups, i.e., groups with the same substitution pattern (these compounds can be labeled as BA2C-type boranes). The synthesis of these symmetric molecules is much simpler (because the same reagents can be used to form the two rings). However, since it can be recognized by those skilled in the art that the A and A' aryl groups have different substitution patterns while having substantially the same electron-withdrawing and steric parameters at the ortho positions, the definition of the substituent should also encompass these obvious equivalents.

[0044] Here, in our experiments, we have found that R6 and R 10 It is noted that BA2C'-type boranes bearing C' aryl groups with two large groups with large steric demands (e.g., Cl, Br, or methyl, see items 4 and 9 below) in the ortho position or BAC2-type substitution patterns have been found to exhibit low activity and / or low selectivity when used for the reduction of ester and lactone compounds. As described in the prior art, the system B(CF5)3 (BA3-type catalyst) bearing only small F substituents in the ortho position cannot reduce common esters or lactones with such selectivity, in contrast to the reduction system of the present invention applying the catalyst of the present invention (see item 1 below).

[0045] During our experiments, we prepared a significant number of catalyst compounds according to the process described in the Examples section. These methods are based on art-known synthetic procedures for the preparation of BAC-type boranes. First, a boronic acid intermediate bearing the C aryl group of the final borane is constructed. This boronic acid is then converted to its respective potassium trifluoroborate salt using potassium bifluoride as the fluoride source. This reaction is generally carried out in a water-methanol solvent mixture at ambient temperature and pressure. The resulting trifluoroborate salts are much more stable than their boronic acid precursors, i.e., they have a longer shelf life and higher air and moisture stability. They also possess the reactivity required for the next synthetic step, which involves reacting the trifluoroborate salt with two equivalents of an aryl Grignard reagent bearing an A aryl group in an ethereal solvent (e.g., diethyl ether or tetrahydrofuran, preferably diethyl ether) to form the respective BAC borane. The reaction temperature can vary within a wide range of values, generally between -78°C and 40°C, preferably between 0°C and 30°C. The applied pressure in these reactions is generally atmospheric. The required Grignard reagents can be prepared from the respective aromatic compounds by several procedures known in the art, such as by directly reacting the respective aryl halide with magnesium metal, by reacting the aryl halide with a transfer Grignard reagent (e.g., isopropylmagnesium chloride) to perform a halogen-magnesium exchange, or by deprotonating the respective aromatic compound using an organolithium reagent (e.g., n-butyllithium) and transmetallating with magnesium bromide to form the Grignard reagent. The final step in the borane synthesis is a purification procedure, which involves solvent exchange into toluene, inert filtration of the precipitate, vacuum evaporation of the toluene filtrate, sonication of the resulting residue in pentane or hexane, and inert filtration of the resulting suspension to obtain the borane as a crystalline powder.

[0046] As seen in Table 1 below, we tested the effectiveness of the prepared catalyst compounds in reactions where methyl 3-phenylpropionate was applied as the ester substrate (see details below). As can be seen, entries 1-9, 13, and 14 were ineffective (low conversion or high conversion with incorrect selectivity, i.e., high conversion with significant overreduction) because they did not have the required substituent pattern. However, entries 10, 11, 12, 15, 16, and 17, which have the substituent pattern according to the present invention, showed excellent conversion and yield with good / acceptable contamination profiles.

[0047] Here, we note that although entries 19 and 20 did not perform really well in this test reaction (yields were low), they can be successfully applied in such reductions where catalysts with weaker Lewis acidic properties are required (see Example 12, where compound 5 (entry 19) was applied as a catalyst and very good results were obtained in the reduction of a more Lewis basic lactone (i.e., γ-butyrolactone), or Example 28, where compound 9 (entry 20) was used as a catalyst and a more reactive silane (i.e., 1,1,3,3-tetramethyldisiloxane) was used as the reducing agent, while the selectivity of the reduction was maintained).

[0048] Furthermore, although item 18 performed poorly in this test reaction (low selectivity), it can be successfully applied in such reductions where a catalyst with stronger Lewis acidic properties is required (see Example 11, where this catalytic compound was applied to give very good results in the reduction of a weakly Lewis basic ester-type substrate, i.e., ethyl 2,2,2-trifluoroacetate).

[0049] These examples demonstrate a further advantage of the catalyst compounds according to the invention, since their Lewis acidity can be adjusted to the required level and adapted to the Lewis basic properties of the substrate (a person skilled in the art knows, on the basis of general knowledge, which substituents increase and which decrease the Lewis acidic / basic properties of the catalyst and of the substrate).

[0050] The test reactions in Table 1 were monitored by quantitative NMR measurements using hexamethylbenzene (HMB) as an internal standard. In particular, a small excess of reducing agent, e.g., TESH (1.1 equivalents), was used to ensure higher or complete conversions and to clarify whether the investigated catalytic systems tended to over-reduce the substrate in the test reactions. Also, the catalyst loading used was higher (1 mol%) than required to ensure shorter reaction times and demonstrate selectivity differences. Using the resulting spectra, we successfully determined the composition of the reaction mixture after 1 h of reaction time (4 h in the case of item 16) for each of the following components: methyl 3-phenylpropionate (ester, starting material, for calculating conversion), triethylsilane (TESH, starting material), triethyl-(1-methoxy-3-phenylpropoxy)silane (silyl acetal, main product, for calculating product yield), triethyl-(3-phenylpropoxy)silane (silyl ether, over-reduction by-product, for monitoring selectivity), and triethylmethoxysilane (TESOMe, over-reduction by-product, for monitoring selectivity). Because TESOMe and silyl ether are formed in the same reaction step, their amounts should be the same. Nevertheless, because the silyl ether can participate in further reactions, monitoring these two components can also provide additional information regarding the selectivity / over-reduction of the reaction. [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5]

[0051] As used herein, D is deuterium, which is an isotope of hydrogen (H) that has the same chemical properties as H, and therefore can replace H without changing the chemistry of the molecule. Obviously, D is also a "group with less steric demands."

[0052] As used herein, the term "alkyl," alone or in combination, refers to an alkyl group having 1 to 20, preferably 1 to 8, and more preferably 1 to 6 or 1 to 5 carbon atoms (i.e., "C 1-6 " or "C 1-5 " alkyl groups), such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, t-butyl, and pentyl groups. In particular cases, the phrase refers to alkyl groups having 1 to 4, or 1 to 3, or 1 to 2 carbon atoms (i.e., "C 1-4 " or "C 1-3 " or "C 1-2 In some cases, the alkyl group may be a methyl group, with methyl being the preferred embodiment.

[0053] As used herein, the term "cycloalkyl" refers to a group formed by removing a hydrogen atom from the ring. 3-8 , preferably C 3-6 It means radicals derived from cycloalkanes, such as cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl radicals.

[0054] As used herein, the term "alkenyl" refers to an aliphatic hydrocarbon group containing at least one carbon-carbon double bond, which may be straight-chained (linear) or branched, and containing 2 to 20, preferably 2 to 10, and more preferably 2 to 6 carbon atoms in the chain. Branched means that one or more lower alkyl groups such as methyl, ethyl or propyl, are attached to a linear alkenyl chain. Non-limiting examples of suitable alkenyl groups include ethenyl (vinyl), propenyl, n-butenyl, 3-methylbut-2-enyl, and n-pentenyl groups.

[0055] As used herein, the term "cycloalkenyl" refers to a C alkyl group containing at least one carbon-carbon double bond (preferably one double bond), such as a cyclobutenyl or cyclopentenyl group. 3-8 , preferably C 4-6 It means a cyclic hydrocarbon group.

[0056] As used herein, the term "aryl", alone or in combination, means a group derived from an aromatic monocyclic or polycyclic ring system containing 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms, more preferably 6 carbon atoms, such as phenyl, naphthyl or azulenyl, especially a phenyl group.

[0057] As used herein, the term "heteroaryl" refers to a group derived from a monocyclic or bicyclic aromatic ring system (fused bicyclic ring system) having 1 to 3 heteroatoms selected from the group consisting of N, O, and S [i.e., the group of N (nitrogen), O (oxygen), or S (sulfur) atoms], and the other ring-forming atoms are carbon atoms. In a preferred embodiment, "heteroaryl" refers to a group derived from a bicyclic aromatic ring system having 1 to 2 heteroatoms selected from the group consisting of O and S, and the other ring-forming atoms are carbon atoms, see, for example, benzofuran and thiophene.

[0058] The above-mentioned alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups may optionally be substituted with one or more substituents [e.g., 1 to 5, or 1 to 4, or 1 to 3, or 1 or 2 substituents selected independently from each other] commonly used in organic chemistry for the substitution of such groups. Thus, the substituents have one or more, preferably 1 to 3, substituents independently selected from the group consisting of halogen, optionally substituted alkyl (more preferably methyl and trifluoromethyl), optionally substituted alkoxy (more preferably methoxy), hydroxyl, alkoxy, haloalkyl, sulfate, amino, amido, acylamino, monoalkylamino, dialkylamino, alkylthio, alkylsulfinyl, and alkylsulfonyl groups. More specific examples include alkyl (more preferably methyl and trifluoromethyl), halogen, hydroxyl, and alkoxy (more preferably methoxy, e.g., fluoro, optionally substituted with halogen), particularly halogen, alkyl, and alkoxy, e.g., alkyl and alkoxy optionally substituted with halogen.

[0059] For the purposes of the present invention, the term "substrate" refers to an ester or lactone (which can be considered a cyclic ester) that reacts with a silane in the presence of a catalyst to give a silyl acetal. The substrate includes saturated or unsaturated esters or lactones. Non-limiting examples of saturated and unsaturated esters are: acetate, trifluoroacetate, propionate, butyrate, isobutyrate, benzoate, dihydrocinnamate, cis-3-hexenoate, 10-undecylenate, 11-eicosenoate, α-eleostearate, oleate, linoleate, esters of naturally occurring saturated and unsaturated fatty acids, such as pheromone precursors, and mixtures thereof. All of the esters cited above may be, for example, alkyl or phenolic esters, such as C1-C 22 , preferably C 16 -C 20 or C 1-6 or C 1-4 or C 1-2They may also be alkyl esters (preferably methyl and ethyl esters, see e.g., ethyl acetate, methyl butyrate, etc.), which are optionally substituted, for example, by aryl, preferably by phenyl (see e.g., 3-phenylpropionate, preferably methyl 3-phenylpropionate). Non-limiting examples of saturated and unsaturated lactones are: butyrolactone, valerolactone, caprolactone, decalactone, dodecalactone.

[0060] As used herein, the term "silyl acetal" refers to a mixed acetal resulting from the hydrosilylation of an ester or lactone substrate. The mixed acetal formed consists of a siloxy group resulting from the silylation of the carbonyl group of the substrate with the respective silane; and an alkoxy group derived from the alkoxy group of the ester or lactone portion of the substrate.

[0061] As mentioned above, the reduction according to the present invention is applicable to a variety of ester and lactone compounds which may contain different functional groups such as unsaturated bonds (one or more non-carbonyl conjugated olefinic double bonds and / or acetylenic triple bonds), alkyl or aryl ethers, amides and halogen groups which would not be affected by the reduction reaction.

[0062] A notable feature of the catalyst according to the present invention is that it allows the reduction of natural triglycerides of fatty acids, such as those forming vegetable oils (e.g., tung oil) and animal fats (e.g., saturated or unsaturated fatty acids having 12 to 24 carbon atoms, preferably 16 to 22 carbon atoms, and in another preferred embodiment, 1 to 5, preferably 1 to 3 double bonds). During the reaction of mixed triglycerides derived from different fatty acids, saturated and unsaturated natural aldehydes can be obtained simultaneously without any modification of the position or stereochemistry of the olefinic double bonds. This is particularly valuable for olefinic bonds with a cis configuration.

[0063] If these substrates contain one or more olefinic groups with a defined stereochemistry (which will generally be cis), the corresponding acetals obtained after reduction according to the present invention will have the same stereochemistry. Thus, oils rich in linoleic and / or linolenic acids, such as linseed oil, will be converted into mixtures rich in linoleyl and / or linolenyl aldehydes.

[0064] Naturally occurring esters of unsaturated fatty acids and monounsaturated alcohols, which are not triglycerides, and in which the chains derived from the fatty acids and alcohols have, independently of one another, 12 to 24 carbon atoms, preferably 16 to 22 carbon atoms, and in another preferred embodiment 1 to 5, preferably 1 to 3 double bonds, such as jojoba oil and sperm oil, can also be reduced according to the present invention without any modification of the position or stereochemistry of the double bonds present in the ester molecules.

[0065] Numerous silanes can be used in the method according to the invention. Such silanes are known to those skilled in the art and will be selected according to their ability to effectively reduce the ester or lactone substrate in the method according to the invention. Non-limiting examples include trialkylsilanes (e.g., triethylsilane), alkoxydialkylsilanes, dialkoxyalkylsilanes, trialkoxysilanes (e.g., trimethoxysilane), dialkylsilanes (e.g., diethylsilane), alkyl or triarylsilanes, diarylsilanes, arylsilanes (e.g., phenylsilane), diarylalkylsilanes, aryldialkylsilanes (e.g., dimethylphenylsilane), arylalkylsilanes (e.g., methylphenylsilane), trisiloxysilanes, arylsilanes (e.g., methylphenylsilane), ... Examples of suitable silanes include silanes, alkyldisiloxysilanes, dialkylsiloxysilanes (e.g., 1,1,3,3-tetramethyldisiloxane (TMDS)), and poly(alkylhydrosiloxane) polymers (preferably poly(methylhydrosiloxane) polymers (PMHS)). The siloxy groups are alkylsiloxy or dialkylsiloxy groups, preferably dimethylsiloxy groups, with the alkyl moiety containing 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and the aryl group is a phenyl or naphthyl group, preferably a phenyl group. In a preferred embodiment of the present invention, the silane is triethylsilane (TESH) or 1,1,3,3-tetramethyldisiloxane (TMDS) due to their availability, availability, and price.

[0066] The catalyst concentration according to the present invention is given in mol % relative to the substrate and is generally between 0.005 and 2.0 mol %, preferably between 0.01 and 1.0 mol %, more preferably between 0.03 and 0.2%. Low catalyst levels are preferred as they reduce the overall cost of catalytic partial reduction.

[0067] Typically, 1.0 mole equivalent of silane compound (e.g., TESH) will be consumed per 1.0 mole of ester or lactone functional group. For practical reasons, it is preferred to use a slight excess of silane compound relative to these stoichiometric amounts, generally on the order of 1 to 15 mol % based on the stoichiometric amount, preferably 2 to 5 mol %. The reduction reaction according to the present invention also occurs when the silane is used in substoichiometric amounts, but this results in a decrease in conversion.

[0068] If a faster reaction is required, the selectivity of the reaction also allows the use of a larger excess of silane (up to 2 equivalents or more), however in these cases the required reaction time is significantly extended (5-10 times) and over-reduction is possible.

[0069] The reduction can be carried out in a solvent such as, for example, an ether (e.g., methyl-tetrahydrofuran, diethyl ether, methyl tert-butyl ether, diisopropyl ether, dibutyl ether, tert-amyl methyl ether, tetrahydrofuran, or dioxane), an aliphatic hydrocarbon (e.g., hexane, heptane, petroleum ether, octane, or cyclohexane), or an aromatic hydrocarbon (e.g., benzene, toluene, xylene, or mesitylene), or a mixture thereof. Low levels of solvent, or even solvent-free systems, can be used. Low levels of solvent include <100% solvent per substrate by weight equivalent (m / m), <50% m / m, <25% m / m, or preferably <10% m / m. Deuterated solvents such as benzene-d6 can also be applied.

[0070] The reaction temperature can vary within a wide range of values, generally within the range of -20°C to 60°C. The temperature selected depends on the reactivity of the substrate and can be adjusted accordingly without difficulty. Preferably, the reaction is carried out at a temperature within the range of 20 to 60°C, preferably 30 to 45°C.

[0071] The pressure applied to the reaction is generally atmospheric, however, elevated pressures (e.g., 2-10 atmospheres) can be useful, especially when one of the components is a gas or a highly volatile compound.

[0072] The order of addition of the reactants is also interchangeable: any two of the components (substrate, catalyst, and silane compound) can be premixed and the third reactant added dropwise.

[0073] The respective aldehyde or lactol is the acid or F of the formed silyl acetal. - The aldehyde can be obtained by (fluoride)-induced hydrolysis. This hydrolysis is known in the art and can be carried out by adding an aqueous or alcoholic solution (or a solution made from a mixture of water and an organic solvent, e.g., acetonitrile or THF) of an acidic reagent, such as acetic acid, HCl, sulfuric acid, or even silica gel, or a fluoride-containing reagent, e.g., TBAF or H2SiF6, to the reaction mixture. The ratio of hydrolysis reagent to silane compound (e.g., TESH) used is approximately 0.01-0.1 mol equivalents. After complete hydrolysis, the formation of two phases is generally observed. The desired aldehyde is typically found in the organic phase and can be obtained by evaporation of any solvents present. If necessary, the resulting residue can be distilled, partitioned between two phases (e.g., hexane / CH3CN), and chromatographed or steam-distilled for further purification (according to the general knowledge of those skilled in the art).

[0074] The hydrolysis is preferably carried out at a temperature within the range of 0 to 100° C., more preferably 10 to 45° C., and even more preferably ambient temperature. The pressure applied to the reaction is generally atmospheric pressure.

[0075] The invention is described in more detail in the following examples, in which temperatures are given in degrees Celsius, yields are given in mol%, chemical shifts for NMR data are given in ppm relative to tetramethylsilane as an internal reference, and abbreviations have their usual meaning in the art.

[0076] example Examples 1-8 and 26 disclose the preparation of compounds of formula (I) shown in Table 1. Other (reference) compounds in Table 1 were synthesized by analogous methods or obtained from commercial sources.

[0077] Example 1 Synthesis of (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 1, see item 12) The compounds were prepared as follows and are shown in Schemes 3-5.

[0078] Step a) Synthesis of (2-bromo-6-fluorophenyl)boronic acid (compound 1a) [ka] In a 500 mL three-neck flask equipped with a condenser, a nitrogen purge inlet, and an inserted digital thermometer, diisopropylamine (8.90 g, 13 mL, 1.1 equiv., 88.0 mmol) was dissolved in tetrahydrofuran (200 mL, abs., N2 purge) and cooled to -78 °C. A solution of butyllithium (5.64 g, 35.2 mL, 1.1 equiv., 88.0 mmol, 2.5 M in hexanes) was added dropwise while maintaining the reaction temperature below -60 °C. The reaction mixture was stirred at -78 °C for 30 minutes. 1-Bromo-3-fluorobenzene (14.0 g, 8.93 mL, 1 equiv., 80.0 mmol) was then added dropwise within 5 minutes while maintaining the reaction temperature below -70 °C. The mixture was stirred at -78 °C for 30 minutes. Trimethyl borate (16.6 g, 18 mL, 2 equiv., 160 mmol) was then added dropwise within 10 min, maintaining the reaction temperature below −70° C. The reaction was then stirred at −78° C. for 30 min, allowed to warm to 25° C., and stirred for an additional 4 h. The reaction mixture was then cooled to 0° C., and 250 mL of 1 M HCl solution (pre-cooled to 0° C.) was added dropwise, maintaining the temperature below 6° C. The reaction was allowed to warm to 25° C. and stirred for an additional 2 h. 160 mL of diethyl ether was then added, and the phases were separated. The aqueous phase was washed with an additional 40 mL of diethyl ether. The combined organic phases were washed with 2×160 mL of brine and dried over NaSO. Finally, the solvent was evaporated on a rotary evaporator to give the crude crystalline product, which could be used in the next synthetic step without further purification.

[0079] Step b) Synthesis of potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) [ka] In a white 1000 mL polypropylene container, (2-bromo-6-fluorophenyl)boronic acid (compound 1a) (17.5 g, 1 equivalent, 80.0 mmol) was measured in and dissolved in methanol (90 mL, technical). Potassium bifluoride (25.0 g, 4 equivalents, 320 mmol) dissolved in water (90 mL) was then added in one portion. The resulting suspension was stirred for 16 hours. 500 mL of acetone was then added, and the reaction mixture was stirred for 30 minutes. The reaction mixture was filtered through filter paper, and the solvent was evaporated on a rotary evaporator at 60 °C. An additional 400 mL of acetone was added and evaporated again to remove traces of water. Finally, 100 mL of toluene was added and evaporated in the same manner. The resulting white powder was again dissolved in 100 mL of acetone and filtered through filter paper. The filtrate was evaporated, and the resulting white powder was mixed with 100 mL of hexane and filtered. The precipitate was washed with 2 × 50 mL of diethyl ether and dried on a rotary evaporator at 60 °C to obtain PO 10 The mixture was kept in a vacuum desiccator using HCl as a desiccant. The product is a white crystalline solid (20.4 g, 72.6 mmol). The combined isolated yield of the first two synthetic steps is 91%. 1 H NMR

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[0080] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 1) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (1.61 g, 2.3 equiv., 66.3 mmol) were measured in iodine and activated with iodine. Then, 20 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (5.21 g, 6.04 mL, 2.3 equiv., 66.3 mmol). The solution was warmed to reflux and began to reflux. 30 mL of diethyl ether was added to dilute the reaction, and the dropwise addition of 2-chloropropane was continued to maintain reflux. In a separate 250 mL two-neck flask, 3-bromo-1,2,4,5-tetrafluorobenzene (15.2 g, 8.07 mL, 2.3 equiv., 66.3 mmol) was measured in 90 mL of abs. diethyl ether, dissolved, and cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe within 45 min, while maintaining the reaction temperature below 5 °C. After the addition was complete, the reaction mixture was stirred for 1 h. In a 500 mL Schlenk flask, potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) (8.10 g, 1 eq., 28.8 mmol) was measured under N2, suspended in 20 mL of abs. diethyl ether, and cooled to 0 °C. The cooled (0 °C) Grignard solution was added via cannula within 20 min, while maintaining the temperature below 4 °C. The reaction mixture was allowed to warm to 25 °C and stirred for an additional 18 h. The solvent was then evaporated in vacuo at 50 °C. Next, 90 mL of abs. toluene was added, and the suspension was sonicated for 10 min. The resulting precipitate was filtered off and washed with 2 × 20 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 70 °C to give an off-white solid. Then 10 mL of abs. pentane was added and the resulting suspension was sonicated and filtered to give the product as a white crystalline powder (6.90 g, 14.3 mmol, 50% yield). 1 H NMR

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[0081] Example 2 Synthesis of (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (Compound 2, see Item 16) The compounds were prepared as follows and are shown in Schemes 3, 4 and 6.

[0082] Step a) and step b) are the same as in Example 1.

[0083] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (Compound 2) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (1.61 g, 2.3 equiv., 66.3 mmol) were measured in iodine and activated with iodine. Then, 20 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (5.21 g, 6.04 mL, 2.3 equiv., 66.3 mmol). The solution was warmed and reflux commenced. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 2-bromo-1,3,4-trifluorobenzene (14.0 g, 7.85 mL, 2.3 equiv., 66.3 mmol) was measured in and dissolved in 90 mL of abs. diethyl ether, which was then cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe over 45 minutes, while maintaining the reaction temperature below 5°C. After the addition was complete, the reaction mixture was stirred for 1 hour. Potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) (8.10 g, 1 equivalent, 28.8 mmol) was measured under N2 in a 500 mL Schlenk flask, suspended in 20 mL of abs. diethyl ether, and cooled to 0°C. The cooled (0°C) Grignard solution was added via cannula within 20 minutes, while maintaining the temperature below 4°C. The reaction mixture was allowed to warm to 25°C and stirred for an additional 18 hours. The solvent was then evaporated in vacuo at 50°C. Next, 90 mL of abs. toluene was added, and the suspension was sonicated for 10 minutes. The resulting precipitate was filtered off and washed with 2 × 20 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 70°C to yield an off-white solid. Then, 10 mL of abs. pentane was added and the resulting suspension was filtered to give the product as a white crystalline powder (8.05 g, 18.0 mmol, 63% yield). 1 H NMR

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[0084] Example 3 Synthesis of (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (compound 3, see entry 11).

[0085] The compounds were prepared as follows and are shown in Schemes 3, 4 and 7.

[0086] Step a) and step b) are the same as in Example 1.

[0087] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (Compound 3) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (1.61 g, 2.3 equiv., 66.3 mmol) were measured in iodine and activated with iodine. Then, 20 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (5.21 g, 6.04 mL, 2.3 equiv., 66.3 mmol). The solution was warmed and reflux began. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 1-bromo-2,3,4,5,6-pentafluorobenzene (16.4 g, 8.27 mL, 2.3 equiv., 66.3 mmol) was measured in 90 mL of abs. diethyl ether, dissolved, and cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe over 45 minutes, while maintaining the reaction temperature below 5°C. After the addition was complete, the reaction mixture was stirred for 1 hour. Potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) (8.10 g, 1 equivalent, 28.8 mmol) was measured under N2 in a 500 mL Schlenk flask, suspended in 20 mL of abs. diethyl ether, and cooled to 0°C. The cooled (0°C) Grignard solution was added via cannula within 20 minutes, while maintaining the temperature below 4°C. The reaction mixture was allowed to warm to 25°C and stirred for an additional 18 hours. The solvent was then evaporated in vacuo at 50°C. Next, 90 mL of abs. toluene was added, and the suspension was sonicated for 10 minutes. The resulting precipitate was filtered off and washed with 2 × 20 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 70°C to yield an off-white solid. Then 10 mL of abs. pentane was added and the resulting suspension was filtered to give the product as a white crystalline powder (5.08 g, 9.79 mmol, 34% yield). 1 H NMR

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[0088] Example 4 Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,4,6-trifluorophenyl)borane (Compound 4, see Item 15) The compounds were prepared as follows and are shown in Schemes 8-10.

[0089] Step a) Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)boronic acid (compound 4a, Pfp = C6F5) [ka] Preparation of i-PrMgCl: A 100 mL three-neck flask was fitted with a reflux condenser and N2 inlet. Magnesium turnings (1.89 g, 1.0 equiv., 77.7 mmol) were weighed and 45 mL of abs. diethyl ether was added. 2-Chloropropane (6.11 g, 7.11 mL, 1.0 equiv., 77.7 mmol) was then added dropwise. The solution was warmed and began to reflux. The dropwise addition of 2-chloropropane was continued to maintain reflux.

[0090] In a 500 mL three-neck flask equipped with a condenser, a nitrogen purge inlet, and an inserted digital thermometer, 2-bromo-2',3,3',4,4',5,5',6,6'-nonafluoro-1,1'-biphenyl (30.7 g, 1.0 equiv., 77.7 mmol) was dissolved in diethyl ether (50 mL, abs., N2 purge) and cooled to 0 °C in an ice bath. The i-PrMgCl solution was added dropwise while maintaining the reaction temperature at 0-5 °C. The reaction mixture was then stirred at 25 °C for 60 min. Trimethyl borate (16.2 g, 17.7 mL, 2.0 equiv., 155 mmol) was then added dropwise within 30 min while maintaining the reaction temperature at 0 °C. The mixture was stirred at 25 °C for an additional 16 h. The reaction was then cooled to 0°C and 80 mL of 1 M HCl solution (pre-cooled to 0°C) was added dropwise, maintaining the temperature below 5°C. The reaction was allowed to warm to 25°C and stirred for an additional 2 hours. 200 mL of diethyl ether was then added and the phases were separated. The aqueous phase was washed with an additional 50 mL of diethyl ether. The combined organic phases were washed with 2 x 160 mL of brine and dried over Na2SO4. Finally, the solvent was evaporated on a rotary evaporator to give the crude product, which could be used in the next synthetic step without further purification.

[0091] Step b) Synthesis of potassium trifluoro(perfluoro-[1,1'-biphenyl]-2-yl)borate (Compound 4b) [ka] In a white 1000 mL polypropylene container, (perfluoro-[1,1'-biphenyl]-2-yl)boronic acid (26.59 g, 77.7 mmol) was measured in methanol (78 mL, technical) and dissolved in methanol. Potassium bifluoride (24.30 g, 4.0 equivalents, 311.11 mmol) dissolved in distilled water (78 mL) was then added in one portion. The resulting suspension was stirred for 16 hours. 500 mL of acetone was then added. The reaction mixture was filtered through filter paper, and the solvent was evaporated on a rotary evaporator at 60 °C. An additional 400 mL of acetone was added and evaporated again to remove traces of water. 100 mL of toluene was then added and evaporated in the same manner. The resulting white powder was again dissolved in 100 mL of acetone and filtered through filter paper. The solvent was evaporated on a rotary evaporator, and the resulting white powder was mixed with 100 mL of hexane, filtered, and then dried at 60 °C. The product is a white, crystalline solid (25.73 g, 63.68 mmol). The isolated yield for this synthetic step is 81.9% equivalent. 19 F NMR

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[0092] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (Compound 4) [ka] A 100 mL three-neck flask equipped with a reflux condenser and N2 inlet was weighed out with magnesium turnings (280 mg, 2.3 equiv., 11.5 mmol). Then, 10 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (903 mg, 1.05 mL, 2.3 equiv., 11.5 mmol). The solution was warmed and reflux began. An additional 10 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 100 mL two-neck flask, 2-bromo-1,3,5-trifluorobenzene (2.43 g, 1.355 mL, 2.3 equiv., 11.5 mmol) was weighed out and dissolved in 40 mL of abs. diethyl ether. The solution was then cooled to 0 °C. The previously prepared i-PrMgCl solution was added dropwise via syringe within 20 min, keeping the reaction temperature below 5 °C. After the addition was complete, the reaction mixture was stirred for 1 h. Potassium trifluoro(perfluoro-[1,1'-biphenyl]-2-yl)borate (compound 4b) (2.11 g, 1 equivalent, 5.00 mmol) was measured under N2 in a 100 mL Schlenk flask, suspended in 5 mL of abs. diethyl ether, and cooled to 0 °C. The chilled (0 °C) Grignard solution was added via cannula within 20 min, keeping the temperature below 5 °C. The reaction mixture was allowed to warm to 25 °C and stirred for an additional 18 h. The solvent was then evaporated in vacuo. Next, 10 mL of abs. toluene was added, and the suspension was sonicated for 10 min. The resulting precipitate was filtered off and washed with 2 × 5 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 45 °C to give an off-white solid. Then 10 mL of abs. pentane was added and the resulting suspension was filtered to give the product as an off-white crystalline powder (1.33 g, 2.27 mmol, 45% yield). 1 H NMR

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[0093] Example 5 Synthesis of (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (Compound 5, see item 19) The compounds were prepared as follows and are shown in Schemes 3, 4 and 11.

[0094] Step a) and step b) are the same as in Example 1.

[0095] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (Compound 5) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (1.61 g, 2.3 equiv., 66.3 mmol) were measured in iodine and activated with iodine. Then, 20 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (5.21 g, 6.04 mL, 2.3 equiv., 66.3 mmol). The solution was warmed and reflux commenced. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 2-bromo-1,3,5-trifluorobenzene (14.0 g, 7.82 mL, 2.3 equiv., 66.3 mmol) was measured in 90 mL of abs. diethyl ether and dissolved therein, which was then cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe over 45 minutes, while maintaining the reaction temperature below 5°C. After the addition was complete, the reaction mixture was stirred for 1 hour. Potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) (8.10 g, 1 equivalent, 28.8 mmol) was measured under N2 in a 500 mL Schlenk flask, suspended in 20 mL of abs. diethyl ether, and cooled to 0°C. The cooled (0°C) Grignard solution was added via cannula within 20 minutes, while maintaining the temperature below 4°C. The reaction mixture was allowed to warm to 25°C and stirred for an additional 18 hours. The solvent was then evaporated in vacuo at 50°C. Next, 90 mL of abs. toluene was added, and the suspension was sonicated for 10 minutes. The resulting precipitate was filtered off and washed with 2 × 20 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 70°C to yield an off-white solid. Then 10 mL of abs. pentane was added and the resulting suspension was filtered to give the product as a white crystalline powder (6.05 g, 13.5 mmol, 47% yield). 1 H NMR

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[0096] Example 6 Synthesis of (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 6, see item 10) The compounds were prepared as follows and are shown in Schemes 12-14.

[0097] Step a) Synthesis of (2-chloro-6-fluorophenyl)boronic acid (compound 6a) [ka] In a 500 mL neck flask equipped with a condenser, a nitrogen purge inlet, and an inserted digital thermometer, 1-chloro-3-fluorobenzene (15.7 mL, 19.142 g, 146.6 mmol) was added to a solution of butyllithium (161.3 mmol) in tetrahydrofuran (117 mL, abs) and hexanes (66 mL, abs) at −75° C. The reaction mixture was stirred at −78° C. for 2 hours. Trimethyl borate (30.47 g, 32.7 mL, 2 equiv., 40.0 mmol) was then added dropwise within 50 minutes, maintaining the reaction temperature below −71° C. The reaction was allowed to warm to 25° C. and then stirred for 16 hours. The reaction was then cooled to 0° C., and 35 mL of 1 M HCl solution (pre-cooled to 0° C.) was added dropwise, maintaining the temperature below 6° C. The reaction was allowed to warm to 25° C. and stirred for an additional 2 hours. The phases were then separated. The aqueous phase was washed with an additional 30 mL of diethyl ether. The combined organic phases were washed with 2 x 30 mL of brine and dried over Na2SO4. Finally, the solvent was evaporated on a rotary evaporator to give a nearly solid, which was washed with hexane and dried. The product was obtained as a white powder (20.76 g, 119.06 mmol). The yield of this synthetic step is 81%. The crude product can be used in the next synthetic step without further purification.

[0098] Step b) Synthesis of potassium (2-chloro-6-fluorophenyl)trifluoroborate (compound 6b) [ka] In a white 1000 mL polypropylene container, (2-chloro-6-fluorophenyl)boronic acid (compound 6a) (20.76 g, 1 equivalent, 119.06 mmol) was measured into and dissolved in methanol (325 mL, technical). Potassium bifluoride (37.2 g, 4 equivalents, 476.22 mmol) dissolved in water (325 mL) was then added in one portion. The resulting suspension was stirred for 16 hours. 300 mL of acetone was then added, and the reaction mixture was stirred for 30 minutes. The reaction mixture was filtered through filter paper, and the solvent was evaporated on a rotary evaporator at 60 °C. 2 × 30 mL of acetone was added and evaporated again to remove traces of water. Finally, 50 mL of toluene was added and evaporated in the same manner. The resulting white powder was again dissolved in 100 mL of acetone and filtered through filter paper. The solvent was evaporated on a rotary evaporator, and the resulting white powder was mixed with 100 mL of hexane and filtered. The filtered material was dried in a rotary evaporator at 60 °C using PO as a desiccant. 10 The mixture was kept in a vacuum desiccator using a vacuum evaporator. The product is a white, crystalline solid (27.00 g, 114.19 mmol). The isolated yield for this synthesis step is 96%. 1 H NMR

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[0099] Step c) Synthesis of (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 6) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (763 mg, 2.3 equiv., 31.4 mmol) were measured in iodine and activated with iodine. Then, 18 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (2.47 g, 2.90 mL, 2.3 equiv., 31.4 mmol). The solution was warmed and reflux commenced. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 3-bromo-1,2,4,5-tetrafluorobenzene (7.19 g, 2.3 equiv., 31.4 mmol) was measured in 95 mL of abs. diethyl ether and dissolved, after which the solution was cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe within 25 min, while maintaining the reaction temperature below 5 °C. After the addition was complete, the reaction mixture was stirred for 1 h. Potassium (2-chloro-6-fluorophenyl)trifluoroborate (compound 6b) (3.84 g, 1 eq., 13.65 mmol) was measured under N2 in a 250 mL Schlenk flask, suspended in 12 mL of abs. diethyl ether, and cooled to 0 °C. The cooled (0 °C) Grignard solution was added via cannula within 20 min, while maintaining the temperature below 4 °C. The reaction mixture was allowed to warm to 25 °C and stirred for an additional 18 h. The solvent was then evaporated in vacuo at 50 °C. Next, 60 mL of abs. toluene was added, and the suspension was sonicated for 10 min. The resulting precipitate was filtered off and washed with 2 × 10 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 70 °C to give an off-white solid. Then 2 x 5 mL of abs. pentane was added and the resulting suspension was filtered to give the product as a white crystalline powder (2.15 g, 4.89 mmol, 36% yield). 1 H NMR

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[0100] Example 7 Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 7, see item 18) The compounds were prepared as follows and are shown in Schemes 8, 9 and 15.

[0101] Step a) and step b) are the same as in Example 4.

[0102] Step c) Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 7) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (671 mg, 2.3 equiv., 27.6 mmol) were measured in iodine and activated with iodine. Then, 20 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (2.17 g, 2.52 mL, 2.3 equiv., 27.6 mmol). The solution was warmed and reflux began. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 3-bromo-1,2,4,5-tetrafluorobenzene (6.32 g, 3.36 mL, 2.3 equiv., 27.6 mmol) was measured in 40 mL of abs. diethyl ether and dissolved therein, which was then cooled to 0 °C. The previously prepared i-PrMgCl solution was added dropwise via syringe within 25 min, while maintaining the reaction temperature below 5 °C. After the addition was complete, the reaction mixture was stirred for 1 h. In a 250 mL Schlenk flask, potassium trifluoro(perfluoro-[1,1'-biphenyl]-2-yl)borate (compound 4b) (5.10 g, 1 equivalent, 12.0 mmol) was measured under N2, suspended in 15 mL of abs. diethyl ether, and cooled to 0 °C. The chilled (0 °C) Grignard solution was added via cannula within 20 min, while maintaining the temperature below 5 °C. The reaction mixture was allowed to warm to 25 °C and stirred for an additional 18 h. The solvent was then evaporated in vacuo. Next, 20 mL of abs. toluene was added, and the suspension was sonicated for 10 min. The resulting precipitate was filtered off and washed with 2 × 15 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 45°C to give an off-white solid. 20 mL of abs. pentane was then added and the suspension was sonicated for 25 minutes. The resulting suspension was filtered to give the product as an off-white crystalline powder (3.26 g, 5.22 mmol, 44% yield). 1 H NMR

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[0103] Example 8 Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,6-trifluorophenyl)borane (Compound 8, see Item 17) The compounds were prepared as follows and are shown in Schemes 8, 9 and 16.

[0104] Step a) and step b) are the same as in Example 4.

[0105] Step c) Synthesis of (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,6-trifluorophenyl)borane (Compound 8) [ka] In a 100 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (648 mg, 2.5 equiv., 25.66 mmol) were measured in iodine and activated with iodine. Then, 25 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (2.09 g, 2.43 mL, 2.5 equiv., 25.66 mmol). The solution was warmed and reflux commenced. An additional 30 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 2-bromo-1,3,4-trifluorobenzene (5.62 g, 3.15 mL, 2.5 equiv., 25.66 mmol) was measured in and dissolved in 40 mL of abs. diethyl ether, which was then cooled to 0 °C. The previously prepared i-PrMgCl solution was added dropwise via syringe within 25 min, while maintaining the reaction temperature below 5 °C. After the addition was complete, the reaction mixture was stirred for 1 h. In a 250 mL Schlenk flask, potassium trifluoro(perfluoro-[1,1'-biphenyl]-2-yl)borate (4.50 g, 1 eq., 10.66 mmol) was measured under N2, suspended in 10 mL of abs. diethyl ether, and cooled to 0 °C. The chilled (0 °C) Grignard solution was added via cannula within 20 min, while maintaining the temperature below 5 °C. The reaction mixture was allowed to warm to 25 °C and stirred for an additional 18 h. The solvent was then evaporated in vacuo. Next, 20 mL of abs. toluene was added, and the suspension was sonicated for 10 min. The resulting precipitate was filtered off and washed with 2 × 15 mL of abs. toluene. The combined filtrates were then evaporated in vacuo at 45 °C to yield an off-white solid. Then, 20 mL of abs. pentane was added and the suspension was sonicated for 25 min. The resulting suspension was filtered to give the product as a white crystalline powder (1.883 g, 3.202 mmol, 30% yield). 1 H NMR

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[0106] Example 9 Tung oil reduction The major fatty acid component of tung oil is alpha-eleostearic acid (82%), which contains one cis-double bond and two trans-double bonds, all conjugated. The isomerization and overreduction of these double bonds is catalyzed by BrF (F 3a Hydrosilylation using )2 borane (compound 2) can avoid direct reduction of triglycerides. [ka]

[0107] The ester, propane-1,2,3-triyl (9Z,9'Z,9''Z,11E,11'E,11''E,13E,13'E,13''E)-tris(octadeca-9,11,13 trienoate) (146 mg, 0.33 equiv., 0.166 mmol) was weighed out in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 [(2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (2.26 mg, 100 μL, 0.05 M in benzene-d6, 0.01 equiv., 5.0 μmol)] was added at room temperature. Triethylsilane (64.4 mg, 89 μL, 1.1 equiv., 0.55 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. Through the complete disappearance of the parent glyceride CH peak ((benzene-d6) δ 4.29 (dd, J = 11.9, 4.1 Hz, 2H), 4.07 (dd, J = 11.9, 6.0 Hz, 2H)) and the appearance of the acetal CH peak ((benzene-d6) δ 5.03-4.93 (m, 2H)). 1 The reaction went to complete conversion as judged by 1 H NMR. 3,3,13,13-tetraethyl-5,11-di((8Z,10E,12E)-heptadeca-8,10,12-trien-1-yl)-8-(((9Z,11E,13E)-1-((triethylsilyl)oxy)octadeca-9,11,13-trien-1-yl)oxy)-4,6,10,12-tetraoxa-3,13-disilapentadecane:

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[0108] The reaction mixture was then diluted with 5 mL of THF and the silyl acetal was hydrolyzed by adding aqueous hydrochloric acid (182 mg, 5.0 mL, 1 M, 10 equiv., 5.0 mmol). After 16 h, the reaction mixture was extracted with 30 mL of ethyl acetate, washed with 30 mL of saturated NaHCO3 solution, dried over MgSO4, and the solvent was removed under reduced pressure. The resulting oil contained α-eleostearoaldehyde (>65 m / m%) as the major component. 1 Based on H NMR, the product also contained trace contaminants from glycerol (<5 m / m%), hexaethyldisiloxane (<25 m / m%), and other fatty acid components of tung oil (<5 m / m%). The aldehydic proton was clearly visible at δ 9.33 (t, J = 1.7 Hz, 1H), while the silyl-acetal peak completely disappeared, indicating total conversion. The double bond remained intact throughout the process, as indicated by the olefinic H peaks ((benzene-d6) δ 6.53 (dd, J = 14.7, 11.2 Hz, 1H), 6.30-6.09 (m, 3H), 5.61 (dt, J = 14.5, 7.1 Hz, 1H), and 5.40 (dt, J = 10.9, 7.7 Hz, 1H)). (9Z,11E,13E)-Octadeca-9,11,13trienal:

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[0109] Example 10 Jojoba Oil Reduction Jojoba oil is composed almost entirely of monoesters (wax esters). Its major fatty acid components are 11 eicosenoic acids containing one double bond, and its major alcoholic components are 11 eicosanols. [ka]

[0110] The ester, icos-11-en-1-yl icos-11-enoate (295 mg, 1 equivalent, 0.500 mmol), was weighed in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 [(2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (2.23 mg, 100 μL, 0.05 M in benzene-d6, 0.01 equivalent, 5.00 μmol)] was added at room temperature. Then, triethylsilane (64.0 mg, 87.8 μL, 1.1 equivalent, 550 μmol) was added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. 1 The reaction was complete as judged by 1 H NMR. Triethyl((1-(icos-11-en-1-yloxy)icos-11-en-1-yl)oxy)silane:

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[0111] The reaction mixture was then diluted with 5 mL of THF and the silyl acetal was hydrolyzed by adding aqueous hydrochloric acid (182 mg, 5.0 mL, 1 M, 10 equiv., 5.0 mmol). After 16 h, the reaction mixture was extracted with 30 mL of ethyl acetate, washed with 30 mL of saturated NaHCO3 solution, dried over MgSO4, and the solvent was removed under reduced pressure. The resulting oil contained icos-11-enal (>55 m / m%) as the major component. 1Based on H NMR, it also contained trace contaminants from 11-eicosanol (<40 m / m%) and hexaethyldisiloxane (<5 m / m%). The aldehydic proton was clearly visible at δ 9.35 (t, J = 1.8 Hz, 1H), while the silyl-acetal peak completely disappeared, indicating total conversion. The double bond remained intact throughout the process, as indicated by the olefinic H peak (benzene-d6) δ 5.48 (t, J = 5.0 Hz, 2H). Icos-11-enal:

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[0112] Example 11 Reduction of ethyl 2,2,2-trifluoroacetate 2,2,2-Trifluoroacetaldehyde is an important synthetic building block in medicinal chemistry. However, the synthesis and use of this compound is challenging due to its low boiling point (20 °C). The use of its silyl acetal as a synthetic precursor could be a viable alternative.

[0113] Silyl acetals can be synthesized starting from the widely available ethyl 2,2,2-trifluoroacetate, but due to the low Lewis basicity of this ester, stronger Lewis acids such as F9(F4)2 borane (compound 7) are required. [ka]

[0114] The ester, ethyl 2,2,2-trifluoroacetate (71.0 mg, 59.5 μL, 1 equiv., 0.500 mmol), was weighed out in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 7, item 18) (2.68 mg, 100 μL, 0.05 M in benzene-d6, 0.01 equiv., 5.00 μmol) was added at room temperature. Then, triethylsilane (116 mg, 160 μL, 2 equiv., 1.00 mmol) was added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. 1 The reaction was complete as judged by 1 H NMR. Product: (1-ethoxy-2,2,2-trifluoroethoxy)triethylsilane (NMR yield 90%) 1 H NMR

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[0115] Example 12 Reduction of γ-butyrolactone The selective reduction of lactones to lactols is a challenging synthetic problem often encountered during the synthesis of several important pharmaceutical intermediates. This also applies to the synthesis of prostaglandins, where reduction of the γ-butyrolactone moiety is a challenging task. The problem of overreduction is even more pronounced in the case of lactones, requiring weaker Lewis acids. This concept is demonstrated in this example, where a borane with weaker Lewis acidity, BrF(Fs)2 borane (compound 5), was used to reduce γ-butyrolactone with high selectivity. [ka]

[0116] In an oven-dried 4 mL vial, the lactone, dihydrofuran-2(3H)-one (86 mg, 76 μL, 1 equiv., 1.0 mmol) was measured under nitrogen and dissolved in 0.8 mL of benzene-d6. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (compound 5, entry 19) (4.4 mg, 0.20 mL, 0.05 M in benzene-d6, 0.01 equiv., 10 μmol) was added at room temperature. Triethylsilane (0.14 g, 0.19 mL, 1.2 equiv., 1.2 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred at room temperature for an additional 16 hours. 1 As judged by H NMR, complete conversion was achieved and the amount of over-reduced by-product (3,3,10,10-tetraethyl-4,9-dioxa-3,10-disiladodecane) was minimal (<12 m / m%). Product: triethyl((tetrahydrofuran-2-yl)oxy)silane (NMR yield 86%) 1 H NMR

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[0117] Example 13 Reduction of methyl 3-phenylpropanoate General method for the hydrosilylation of methyl 3-phenylpropanoate esters using catalysts according to the present invention (Scheme 1, Table 1) The reaction was carried out under inert conditions using neat or dry solvents. Importantly, the catalyst can function even in the presence of small amounts of water (technical grade solvents).

[0118] In an oven-dried 20 mL vial, the ester substrate, methyl 3-phenylpropanoate (0.82 g, 0.79 mL, 1 equiv., 5.0 mmol), was measured and dissolved in 9 mL of abs. toluene. Next, a solution of the catalyst in toluene ((2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2, entry 16) (23 mg, 1.0 mL, 0.05 M in toluene, 0.01 equiv., 50 μmol)) was added at room temperature. Triethylsilane (0.64 g, 0.88 mL, 1.1 equiv., 5.5 mmol) was then added dropwise to the stirring reaction mixture. Immediately, the reaction began to warm, and evolution of a small amount of hydrogen gas was observed (from traces of water / alcohol / carboxylic acid). The reaction was further stirred at room temperature for 16 h until conversion of the ester was complete, as determined by NMR or GC-MS. The reaction mixture was then passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product, triethyl(1-methoxy-3-phenylpropoxy)silane (1.39 g, 4.95 mmol, 99% yield).

[0119] The above method can be applied using other catalyst compounds shown in Table 1, and the necessary modifications are within the general knowledge of a person skilled in the art. 1 H NMR

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[0120] Example 14 Reduction of ethyl 4-bromobutanoate [ka] The ester, ethyl 4-bromobutanoate (2.93 g, 2.15 mL, 1 equiv., 15.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (6.70 mg, 300 μL, 0.05 M in benzene-d6, 0.001 equiv., 15.0 μmol) was added at room temperature. Triethylsilane (2.27 g, 3.1 mL, 1.3 equiv., 19.5 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (4-bromo-1-ethoxybutoxy)triethylsilane (4.54 g, 14.6 mmol, 97% yield). 1 H NMR

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[0121] Example 15 Reduction of ethyl 3-bromopropanoate [ka] The ester, ethyl 3-bromopropanoate (3.62 g, 2.55 mL, 1 equiv., 20.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (8.94 mg, 400 μL, 0.001 equiv., 20.0 μmol) was added at room temperature. Triethylsilane (2.56 g, 3.51 mL, 1.1 equiv., 22.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (3-bromo-1-ethoxypropoxy)triethylsilane (6.2 g, 21 mmol, 99+% yield). 1 H NMR

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[0122] Example 16 Reduction of ethyl 5-bromopentanoate [ka] The ester, ethyl 5-bromopentanoate (4.18 g, 3.17 mL, 1 equiv., 20.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (8.94 mg, 400 μL, 0.05 M in benzene-d6, 0.001 equiv., 20.0 μmol) was added at room temperature. Triethylsilane (2.56 g, 3.51 mL, 1.1 equiv., 22.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: ((5-bromo-1-ethoxypentyl)oxy)triethylsilane (6.5 g, 20 mmol, 99+% yield). 1 H NMR

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[0123] Example 17 Reduction of ethyl 6-bromohexanoate [ka] The ester, ethyl 6-bromohexanoate (3.35 g, 2.67 mL, 1 equiv., 15.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (6.70 mg, 300 μL, 0.05 M in benzene-d6, 0.001 equiv., 15.0 μmol) was added at room temperature. Triethylsilane (1.92 g, 2.64 mL, 1.1 equiv., 16.5 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: ((6-bromo-1-ethoxyhexyl)oxy)triethylsilane (4.9 g, 14 mmol, 96% yield). 1 H NMR

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[0124] Example 18 Reduction of isopropyl 4-bromobutanoate [ka] The ester, isopropyl 4-bromobutanoate (2.09 g, 1 equiv., 10.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (4.47 mg, 200 μL, 0.05 M in benzene-d6, 0.001 equiv., 10.0 μmol) was added at room temperature. Triethylsilane (1.28 g, 1.76 mL, 1.1 equiv., 11.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (4-bromo-1-isopropoxybutoxy)triethylsilane (2.84 g, 8.73 mmol, 87% yield). 1 H NMR

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[0125] Example 19 Reduction of ethyl 2-(2-chloroethoxy)acetate [ka] The ester, ethyl 2-(2-chloroethoxy)acetate (1.67 g, 1 equiv., 10.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (4.47 mg, 200 μL, 0.05 M in benzene-d6, 0.001 equiv., 10.0 μmol) was added at room temperature. Triethylsilane (1.28 g, 1.76 mL, 1.1 equiv., 11.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (2-(2-chloroethoxy)-1-ethoxyethoxy)triethylsilane (2.5 g, 8.8 mmol, 88% yield). 1 H NMR

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[0126] Example 20 Reduction of methyl 2-bromopropanoate [ka] The ester, methyl 2-bromopropanoate (1.67 g, 1.12 mL, 1 equiv., 10.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (4.47 mg, 200.0 μL, 0.05 M in benzene-d6, 0.001 equiv., 10.0 μmol) was added at room temperature. Triethylsilane (1.28 g, 1.76 mL, 1.1 equiv., 11.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give (2-bromo-1-methoxypropoxy)triethylsilane (2.7 g, 9.5 mmol, 95% yield). The product is a mixture of possible diastereomers in a 3:1 ratio. 1 H NMR Major diastereomers:

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[0127] Example 21 Reduction of ethyl 2-(2-bromoethoxy)acetate [ka] The ester, ethyl 2-(2-bromoethoxy)acetate (2.11 g, 1 equiv., 10.0 mmol), was weighed in an oven-dried 20 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (44.7 mg, 2.00 mL, 0.05 M in benzene-d6, 0.01 equiv., 100 μmol) was added at room temperature. Triethylsilane (1.40 g, 1.92 mL, 1.2 equiv., 12.0 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (2-(2-bromoethoxy)-1-ethoxyethoxy)triethylsilane (3.2 g, 9.8 mmol, 98% yield). 1 H NMR

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[0128] Example 22 Reduction of ethyl 4-bromo-2-fluorobutanoate [ka] The ester, ethyl 4-bromo-2-fluorobutanoate (533 mg, 1 equiv., 2.50 mmol), was weighed in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (11.2 mg, 500 μL, 0.05 M in benzene-d6, 0.01 equiv., 25.0 μmol) was added at room temperature. Triethylsilane (349 mg, 479 μL, 1.2 equiv., 3.00 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (4-bromo-1-ethoxy-2-fluorobutoxy)triethylsilane (720 mg, 2.19 mmol, 88% yield). 1 H NMR

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[0129] Example 23 Reduction of ethyl decanoate [ka] The ester, ethyl decanoate (40.0 g, 1 equiv., 200 mmol), was measured under nitrogen in an oven-dried 500 mL flask and dissolved in 200 mL of dry toluene. Next, a solution of the catalyst in toluene (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (89.2 mg, 3.99 mL, 0.05 M in toluene, 0.001 equiv., 200 μmol) was added at room temperature. Triethylsilane (25.5 g, 35.1 mL, 1.1 equiv., 220 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: ((1-ethoxydecyl)oxy)triethylsilane (62 g, 0.20 mol, 98% yield). 1 H NMR

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[0130] Example 23 Reduction of ethyl 4-bromopentanoate [ka] The ester, ethyl 4-bromopentanoate (1.05 g, 1 equiv., 5.00 mmol), was weighed in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in toluene (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (2.23 mg, 100 μL, 0.05 M in toluene, 0.001 equiv., 5.00 μmol) was added at room temperature. Triethylsilane (698 mg, 958 μL, 1.2 equiv., 6.00 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: ((4-bromo-1-ethoxypentyl)oxy)triethylsilane (1.6 g, 4.9 mmol, 98% yield). 1 H NMR

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[0131] Example 24 Reduction of ethyl 4-bromo-2,2-difluorobutanoate [ka] The ester, ethyl 4-bromo-2,2-difluorobutanoate (578 mg, 1 equiv., 2.50 mmol), was weighed in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in toluene (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 1) (24.1 mg, 1.00 mL, 0.05 M in toluene, 0.02 equiv., 50.0 μmol) was added at room temperature. Triethylsilane (349 mg, 479 μL, 1.2 equiv., 3.00 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give the product: (4-bromo-1-ethoxy-2,2-difluorobutoxy)triethylsilane (448 mg, 1.29 mmol, 52% yield). 1 H NMR

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[0132] Example 25 Reduction of ethyl 4-bromo-2-methylbutanoate [ka] The ester, ethyl 4-bromo-2-methylbutanoate (1.05 g, 1 equiv., 5.00 mmol), was weighed in an oven-dried 4 mL vial under nitrogen. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (compound 2) (11.2 mg, 500 μL, 0.05 M in benzene-d6, 0.005 equiv., 25.0 μmol) was added at room temperature. Triethylsilane (698 mg, 958 μL, 1.2 equiv., 6.00 mmol) was then added dropwise to the reaction mixture with stirring. The reaction was stirred overnight. The reaction was completely converted as determined by 1H NMR. The next day, the reaction mixture was passed through a short pad of silica and eluted with hexane. The filtrate was concentrated in vacuo to give (4-bromo-1-ethoxy-2-methylbutoxy)triethylsilane (1.48 g, 4.55 mmol, 91% yield). The product is a mixture of possible diastereomers in a 3:2 ratio. 1 H NMR Major diastereomers:

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[0133] Example 26 Synthesis of (2-bromo-6-fluorophenyl)bis(2,6-difluorophenyl)borane (Compound 9, see item 20) The compounds were prepared as follows and are shown in Schemes 3, 4 and 34.

[0134] Step a) and step b) are the same as in Example 1.

[0135] Step c) Synthesis of (2-bromo-6-fluorophenyl)bis(2,6-difluorophenyl)borane (Compound 9) [ka] Scheme 34 In a 50 mL three-neck flask equipped with a reflux condenser and N2 inlet, magnesium turnings (0.95 g, 2.2 equiv., 39.2 mmol) were measured in iodine and activated with iodine. Then, 15 mL of abs. diethyl ether was added, followed by the dropwise addition of 2-chloropropane (3.08 g, 3.57 mL, 2.2 equiv., 39.2 mmol). The solution was warmed and reflux commenced. An additional 15 mL of diethyl ether was added, and the dropwise addition of 2-chloropropane continued to maintain reflux. In a separate 250 mL two-neck flask, 2-bromo-1,3-difluorobenzene (7.56 g, 4.42 mL, 2.2 equiv., 39.2 mmol) was measured in 60 mL of abs. diethyl ether and dissolved therein, which was then cooled to 0 °C. The previously prepared Grignard solution was added dropwise via syringe over 45 minutes, while maintaining the reaction temperature below 5°C. After the addition was complete, the reaction mixture was stirred for 1 hour. Potassium (2-bromo-6-fluorophenyl)trifluoroborate (compound 1b) (5.00 g, 1 equivalent, 17.8 mmol) was measured under N2 in a 250 mL Schlenk flask, suspended in 10 mL of abs. diethyl ether, and cooled to −78°C. The cooled (−78°C) Grignard solution was added via cannula within 20 minutes, while maintaining the temperature below −60°C. The reaction mixture was allowed to warm to 25°C and stirred for an additional 18 hours. The solvent was then evaporated in vacuo at 50°C. Next, 60 mL of abs. toluene was added, and the suspension was sonicated for 10 minutes. The resulting precipitate was filtered off and washed with 2 × 10 mL of abs. toluene. The combined filtrate was then evaporated in vacuo at 70° C. to give an off-white solid. 20 mL of hexane was then added and the resulting suspension was filtered at −78° C. to give the product as a white crystalline powder (2.92 g, 7.10 mmol, 40% yield). 1 H NMR

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[0136] Example 27 Alternative reduction of ethyl 4-bromobutanoate using TMDS [ka] In an oven-dried 20 mL vial, the ester, ethyl 4-bromobutanoate (1.29 g, 0.95 mL, 1 equiv., 6.60 mmol), was measured under nitrogen and dissolved in 6.6 mL of abs. toluene. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (compound 5) (2.95 mg, 132 μL, 0.05 M in benzene-d6, 0.001 equiv., 6.60 μmol) was added at room temperature. Then, with stirring, 1,1,3,3-tetramethyldisiloxane (TMDS) (532 mg, 0.70 mL, 0.6 equiv., 3.96 mmol) was added dropwise to the reaction mixture. The reaction was stirred overnight. The reaction was completely converted as determined by H NMR. The next day, the solvent was evaporated and the crude product was purified using flash chromatography on silica gel with a hexane / ethyl acetate gradient elution. After chromatography, the product-containing fractions were concentrated in vacuo to give the product, 4,10-bis(3-bromopropyl)-6,6,8,8-tetramethyl-3,5,7,9,11-pentaoxa-6,8-disilatridecane (1.64 g, 3.13 mmol, 95% yield). 1 H NMR

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[0137] Example 28 Reduction of ethyl 3-phenylpropanoate with TMDS [ka] In an oven-dried 20 mL vial, the ester, ethyl 3-phenylpropanoate (1.07 g, 1 equivalent, 6.00 mmol), was measured under nitrogen and dissolved in 6.0 mL of abs. toluene. Next, a solution of the catalyst in benzene-d6 (2-bromo-6-fluorophenyl)bis(2,6-difluorophenyl)borane (compound 9) (2.47 mg, 120 μL, 0.05 M in benzene-d6, 0.001 equivalent, 6.00 μmol) was added at room temperature. Then, with stirring, 1,1,3,3-tetramethyldisiloxane (TMDS) (467 mg, 0.62 mL, 0.58 equivalent, 3.48 mmol) was added dropwise to the reaction mixture. The reaction was stirred overnight. The reaction was completely converted as determined by H NMR. The next day, the solvent was evaporated, and the crude product was purified using flash chromatography on silica gel with a hexane / ethyl acetate gradient elution. After chromatography, the product-containing fractions were concentrated in vacuo to give the product 6,6,8,8-tetramethyl-4,10-diphenethyl-3,5,7,9,11-pentaoxa-6,8-disilatridecane (1.15 g, 2.33 mmol, 78% yield). 1 H NMR

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[0138] General Notes The following theoretical assumptions can be made during the evaluation / explanation of the results. First, steric factors should be taken into account, since ortho-substituents on the aryl ring significantly hinder access to the boron center. Thus, the principle of size exclusion is realized, the essence of which is that borane does not form stable adducts with Lewis basic components present in the reaction mixture, while triethylsilane still has access to them. This improves selectivity, but significant steric "crowding" can result in a decrease in reactivity. Another important factor is the Lewis acidity of the borane. Increasing it increases reactivity up to a certain level, but above this level, electron-withdrawing substituents overly stabilize the hydride intermediate that forms, thereby reducing its reactivity. However, increasing the reactivity of the borane can also decrease selectivity. A further aspect is the reactivity of the substrate (ester or lactone) to be reduced. In the case of a reactive substrate, the less reactive catalyst of the present invention may be appropriate, and vice versa. The selection of an appropriate catalyst for a particular substrate requires "fine-tuning" the catalyst's substituent pattern (increasing or decreasing its Lewis acidity by using substituents that provide the desired electron-withdrawing effect). The theoretical selection can be made based on the predictable knowledge of a person skilled in the art, and the success of the selected substituent pattern can be confirmed by relatively simple experimentation, i.e., without imposing an undue burden on a person skilled in the art working in this field. This is a very important feature of the present invention that allows for the general use of the catalyst family of the present invention.

Claims

1. A compound of general formula (I). 【Chemical 1】 (In the formula, B is boron; Ring A and ring A′ are each independently an aryl or heteroaryl group; R １ and R' １ are independently selected from groups with small steric demands, preferably H, D and F; R ５ and R' ５ are independently selected from groups with small steric demands, preferably H, D and F; Each R ２ , R ３ , R ４ , R' ２ , R' ３ and R' ４ are H, D, F, Cl, Br, I, SF ５ , independently selected from the group consisting of alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, wherein said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; Ring C is an aryl group; R ６ is selected from groups with small steric demands, preferably H, D and F; R １０ is a group with high steric demand, preferably Cl, Br, I, SF ５ , alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl and Si(R １５ ) ３ R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; １５ The groups are, independently of one another, selected from the following range: alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups being optionally substituted; R ７ , R ８ and R ９ are independently H, D, F, Cl, Br, I, SF ５ , alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; however, R １ From R ５ , R' １ From R' ５ and R ６ From R ９ If F, then R １０ is not a pentafluorophenyl group or a methyl group; R １ From R ５ , R' １ From R' ５ and R ６ ~R ９ is H, then R １０ is not phenyl; R １ From R ５ , R' １ From R' ５ is F and R ６ From R ９ is H, then R １０ is not methyl; R １ From R ５ , R' １ , R' ３ , R' ４ , R' ５ , R ６ , R ７ , R ８ is H and R' ２ and R ９ When is Br, R １０ is not Cl; R １ , R ５ , R １ ' and R ５ ' is H and R ２ , R ４ , R ２ ' and R ４ ' is CF ３ and R ６ and R ８ is F and R ７ and R ９ is H, then R １０ is not Cl; R １ , R ５ , R １ ' and R ５ ' is H, R ２ , R ４ , R ２’ , R ４’ , R ６ and R ９ is CF ３ If R １０ is not H; R １ , R ２ , R ４ , R ５ , R １’ R ２’ , R ４’ and R ５’ is F, R ３’ , R ３ , R ６ , R ７ and R ８ is H and R ９ When is Cl, R １０ is not 2-Br-phenyl; R １ , R ２ , R ４ , R ５ , R １’ R ２’ , R ４’ and R ５’ is F, R ３’ , R ３ , R ６ , R ７ , R ８ and R ９ is H, then R １０ is CF ３ isn't it)

2. Use of compounds of general formula (I). 【Chemistry 2】 (In the formula, B is boron; Ring A and ring A′ are each independently an aryl group; R １ and R' １ are independently selected from groups with small steric demands, preferably H, D and F; R ５ and R' ５ are independently selected from groups with small steric demands, preferably H, D and F; Each R ２ , R ３ , R ４ , R' ２ , R' ３ and R' ４ are H, D, F, Cl, Br, I, SF ５ , independently selected from the group consisting of alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, wherein said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; Ring C is an aryl group; R ６ is selected from groups with small steric demands, preferably H, D and F; R １０ is a group with high steric demand, preferably Cl, Br, I, SF ５ , alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl and Si(R １５ ) ３ R is selected from the group consisting of alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups, wherein the alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl, and heteroaryl groups are optionally substituted; １５ The groups are, independently of one another, selected from the following range: alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups being optionally substituted; R ７ , R ８ and R ９ are independently H, D, F, Cl, Br, I, SF ５ , alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups, wherein said alkyl, cycloalkyl, alkenyl, cycloalkenyl, aryl and heteroaryl groups are optionally substituted; The substrate optionally contains one or more functional groups independently selected from the group consisting of non-carbonyl conjugated olefinic bonds, non-carbonyl conjugated acetylenic bonds, ethers, amides, and halogen groups as catalysts for the partial reduction of carbonyl groups in ester or lactone substrates.

3. The compound of formula (I) is characterized by the general formula (Ia): 【Chemistry 3】 (In the ceremony Rings X and X′ are phenyl groups; R １ and R' １ is independently selected from the group consisting of H, D, and F; R ５ and R' ５ is independently selected from the group consisting of H, D, and F; Each R ２ , R ３ , R ４ , R' ２ , R' ３ and R' ４ are independently selected from the group consisting of H, D, F, Cl, Br, alkyl, cycloalkyl, and aryl groups, wherein said alkyl, cycloalkyl, and aryl groups are optionally substituted; The Y ring is a phenyl group; R ６ is selected from the group consisting of H, D and F; R １０ are Cl, Br, I, SF ５ , alkyl, cycloalkyl, and aryl groups, wherein said alkyl, cycloalkyl, and aryl groups are optionally substituted; R ７ , R ８ and R ９ are independently selected from the group consisting of H, D, F, Cl, Br, alkyl and cycloalkyl groups, wherein said alkyl and cycloalkyl groups are optionally substituted. A compound according to claim 1 or a use according to claim 2.

4. The rings X and X′ are phenyl groups, and each R １ , R' １ , R ５ and R' ５ is F; and each R ２ , R ３ R ４ , R' ２ , R' ３ and R' ４ is independently selected from H and F; The Y ring is a phenyl group, and R ６ is selected from H and F; R １０ is selected from Cl, Br, methyl and pentafluorophenyl groups; R ７ , R ８ and R ９ is independently selected from H and F; 4. A compound or use according to claim 3.

5. 5. The compound or use according to claim 3 or 4, wherein X and X' are independently selected from the group consisting of pentafluorophenyl, 2,3,4,6-tetrafluorophenyl, 2,3,5,6-tetrafluorophenyl, 2,4,6-trifluorophenyl, 2,3,6-trifluorophenyl and 2,6-difluorophenyl groups.

6. The compound or use according to any one of claims 3 to 5, wherein Y is selected from the group consisting of 2-chloro-6-fluorophenyl, 2-bromo-6-fluorophenyl and perfluoro-1,1'-biphenyl-2-yl groups.

7. The compound of general formula (I) is the following compound: (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 1); (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (Compound 2); (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (compound 3); (Perfluoro-[1,1′-biphenyl]-2-yl)bis(2,4,6-trifluorophenyl)borane (Compound 4); (2-bromo-6-fluorophenyl)bis(2,4,6-trifluorophenyl)borane (compound 5); (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (compound 6); and (Perfluoro-[1,1′-biphenyl]-2-yl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 7); Perfluoro-[1,1'-biphenyl]-2-yl)bis(2,3,6-trifluorophenyl)borane (Compound 8) 7. A compound or use according to any one of claims 3 to 6, selected from the group consisting of:

8. The compound of general formula (I) is the following compound: (2-bromo-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 1); (2-bromo-6-fluorophenyl)bis(2,3,6-trifluorophenyl)borane (Compound 2); (2-bromo-6-fluorophenyl)bis(perfluorophenyl)borane (compound 3); (perfluoro-[1,1′-biphenyl]-2-yl)bis(2,4,6-trifluorophenyl)borane (compound 4); and (2-chloro-6-fluorophenyl)bis(2,3,5,6-tetrafluorophenyl)borane (Compound 6) 8. The compound or use according to claim 7, selected from the group consisting of:

9. 1. A method for preparing an aldehyde or lactol by partial reduction of a carbonyl group in an ester or lactone substrate, wherein the substrate optionally contains one or more functional groups independently selected from the group consisting of a non-carbonyl conjugated olefinic bond, a non-carbonyl conjugated acetylenic bond, an ether, an amide, and a halogen group, said method comprising the steps of: a) reacting the ester or lactone substrate with a silane in the presence of a catalytic amount of a compound of formula (I) as defined in any one of the preceding claims to form a silyl acetal; b) hydrolyzing the resulting silyl acetal with one or more acidic or fluoride-containing reagents to form an aldehyde or lactol; c) optionally isolating and purifying the resulting aldehyde or lactol; A method comprising:

10. A compound of general formula (II): 【Chemistry 4】 (In the formula, X is a halogen selected from the group consisting of Cl and Br; E is (CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ wherein m is an integer from 2 to 12, and n and p are each independently an integer from 1 to 5; ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ any one of the methylene groups may be optionally substituted with one or more substituents independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl or trifluoromethyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R １１ is a trialkylsilyl or dialkylsiloxysilyl group, the alkyl portion of which is optionally substituted C １－６ Alkyl group, preferably C １－４ is an alkyl group; R １２ is an optionally substituted alkyl group, preferably C １－６ Alkyl group, preferably C １－３ alkyl group)

11. X is a halogen selected from the group consisting of Cl and Br; E is (CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ wherein m is an integer from 2 to 10, and n and p are each independently an integer from 1 to 3, ((CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ any one of the methylene groups may be optionally substituted with 1 to 3 substituents independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R １１ is a trialkylsilyl or dialkylsiloxysilyl group, and the alkyl portion is C １－２ an alkyl group, preferably a triethylsilyl or dimethylsiloxysilyl group; R １２ is C １－３ an alkyl group, preferably a methyl, ethyl, propyl or isopropyl group; A compound of formula (II) according to claim 10.

12. The following compounds: (4-Bromo-1-ethoxybutoxy)triethylsilane (Example 14) (3-Bromo-1-ethoxypropoxy)triethylsilane (Example 15) ((5-Bromo-1-ethoxypentyl)oxy)triethylsilane (Example 16) ((6-Bromo-1-ethoxyhexyl)oxy)triethylsilane (Example 17) (4-Bromo-1-isopropoxybutoxy)triethylsilane (Example 18) (2-(2-chloroethoxy)-1-ethoxyethoxy)triethylsilane (Example 19) (2-(2-Bromoethoxy)-1-ethoxyethoxy)triethylsilane (Example 21) (4-Bromo-1-ethoxy-2-fluorobutoxy)triethylsilane (Example 22) ((4-Bromo-1-ethoxypentyl)oxy)triethylsilane (Example 24) (4-Bromo-1-ethoxy-2,2-difluorobutoxy)triethylsilane (Example 25) (4-Bromo-1-ethoxy-2-methylbutoxy)triethylsilane (Example 26) 12. A compound of formula (II) according to claim 10 or 11, selected from the group consisting of:

13. A compound of general formula (III): 【Chemistry 5】 (In the formula, X is a halogen selected from the group consisting of Cl and Br; G is (CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ wherein m is an integer from 2 to 12, n and p are each independently an integer from 1 to 5, and (CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ any one of the methylene groups may be optionally substituted with one or more substituents [e.g., 1 to 5, or 1 to 4, or 1 to 3, or 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl or trifluoromethyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R １３ is an optionally substituted alkyl group, preferably C １－３６ an alkyl group, more preferably a methyl group; R １４ is an optionally substituted alkyl group, preferably C １－６ Alkyl group, preferably C １－３ alkyl group)

14. X is a halogen selected from the group consisting of Cl and Br; G is (CH ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ wherein m is an integer from 2 to 10, and n and p are each independently an integer from 1 to 3; ２ ) ｍ or (CH ２ ) ｎ -O-(CH ２ ) ｐ any one of the methylene groups may be optionally substituted with 1 to 3 substituents [e.g., 1 or 2 substituents] independently selected from the group consisting of halogen, an optionally substituted alkyl group (preferably a methyl group), or an optionally substituted alkoxy group (preferably a methoxy group); R １３ is C １－３ an alkyl group, preferably a methyl group; R １４ is C １－３ an alkyl group, preferably a methyl, ethyl, propyl or isopropyl group; 14. A compound of formula (III) according to claim 13.

15. The compound of formula (III) according to claim 13 or 14, which is 4,10-bis(3-bromopropyl)-6,6,8,8-tetramethyl-3,5,7,9,11-pentaoxa-6,8-disilatridecane (Example 27).

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